<Item type="Member" action="add" id="@1">
  <source_id>
    <Item type="Identity" action="get" select="id">
      <keyed_name>@2</keyed_name>
    </Item>
  </source_id>
  <related_id>
    <Item type="Identity" action="get" select="id">
      <keyed_name>@3</keyed_name>
    </Item>
  </related_id>
</Item>